The present invention relates generally to the machining of mold pins and, more particularly, to a fixture for retaining workpieces for separate cut-off and precision grinding operations, facilitating the efficient machining of quantities of mold pins to close tolerances.
Mold pins, such as punch pins, ejector pins and core pins, are employed in large numbers and in a wide variety of sizes and shapes. Multiple copies of the same mold pin configuration are often required, so that the same precision machining operations are repeated over and over.
Hardened steel pin blanks, of precise diameters ranging from very small diameters to one and one-half inches, and ranging in length to twelve inches and longer, are obtained from a manufacturer. The pin blanks have an elongated cylindrical shaft, and an enlarged mounting head. The pin blanks are then precision-cut by a machinist to desired lengths. Normally, a batch of pins is made at one time. The cutting to length must be very precise, with a precise, flat grind on the end.
Making pins from a blank typically involves two steps: First, an initial rough cut is made, employing a cut-off wheel to establish the approximate length. Then, a final precision grinding operation is performed, to establish the final length and to make the end flat.
Traditionally, machinists make these pins employing a variety of clamps, but no particularly efficient technique is generally used. Typically, a simple V-block fixture is held in a vice.
Specialized fixtures for machining mold pins are disclosed for example in Jaskolski U.S. Pat. No. 4,650,379 and Lehman U.S. Pat. No. 5,377,963. While the Jaskolski and Lehman fixtures are perhaps of some benefit, there nevertheless remains a need for a fixture which facilitates efficient machining of mold pins in a wide variety of sizes and configurations.